The objective of the proposed research is to determine the role hormones play in aggressive and in other behaviors of mice. The research will take three paths. First, an assessment of the effect of uterine position relative to male fetuses upon females will be made. A number of sexually dimorphic behaviors will be studied. Second, the ability of estrogen to mimick testosterone with respect to its aggression-activating property will be determined. And third, an attempt will be made to determine whether stress experienced by a pregnant animal can influence the later aggressive behavior of its male and female offspring. In addition, the effect upon aggression of the synthetic corticoid hormone prednisone will be studied.